Income Taxes (Summary Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Net operating loss carryforwards	$ 17,897	$ 40,729
Tax credit carryforwards	5,516	3,970
Deferred revenue, accruals and reserves	70,539	73,847
Other	7,401	6,724
Total deferred tax assets	101,353	125,270
Valuation allowance	(6,598)	(10,153)
Net deferred tax assets	94,755	115,117
Property and equipment	(3,466)	(2,764)
Other	(3,608)	(7,495)
Deferred Tax Liabilities, Gross	(7,074)	(10,259)
Total deferred tax assets	$ 87,681	$ 104,858